Since any lens of 75/85/90mm focal length is difficult to focus accurately and consistently on a rangefinder like the Leica M9, the f/4 maximum aperture is less of a real-world limitation that it might seem, at least for many types of photography.

Taking the relatively low price into account, the 85/4 might be a great choice for a compact kit where telephoto capability is needed.

The near-zero distortion and very high imaging quality make it eminently suitable for true-to-life imagery.

Focusing

Like all lenses over 50mm, the key challenge on a rangefinder like the Leica M9 will be accurate focus and framing, just as with the Leica 75mm f/2 APO-Summicron-M. In essence, perfect 20/20 vision is needed, along with perfect rangefinder focus adjustment. Leica M9/M7/M8 users should consider the Viewfinder Magnifier 1.4X for use with 75/85/90mm lenses.